1. Field of the Invention
The present invention relates to a belt type transmission used in a transmission of, for example, a motorcycle, with the speed thereof being automatically changed. More specifically, the present invention relates to a support structure of a fixed pulley piece of a driven pulley of the belt type transmission.
2. Description of the Background Art
A motorcycle comprising a V-belt type transmission is heretofore disclosed in Japanese Patent Publication No. Hei 5-47437. In this transmission, a V-pulley on the driven side, to which power from a V-pulley on the driving side fitted to a crankshaft is transmitted via a V-belt, is rotatably supported on a support shaft that is pivotally supported rotatably at the opposite ends on an outside wall of a transmission case having the transmission built therein and on an inside wall towards the rear wheel. That is to say, of a fixed pulley and a movable pulley constituting the V-pulley on the driven side, the fixed pulley is provided with a support barrel secured thereon, and the opposite ends of the support barrel are rotatably supported on the support shaft via a pair of bearings, to thereby make the fixed pulley rotatable with respect to the support shaft.
However, with the conventional transmission, load from the driven pulley is imposed only on the support shaft (driven shaft). As a result, a large load acts on the support portion of the transmission case that rotatably supports the support shaft, and hence the support portion is likely to wear out, and there is room for improvement in view of the durability.
The invention of this application has been completed in view of the above situation, and it is an object of the invention according to a first aspect to reduce the load acting on the driven shaft to improve the durability of the support portion of the driven shaft. It is also an object of the invention according to a second aspect to improve the durability of the bearing supporting the fixed pulley piece on the driven side. Moreover, it is an object of the invention according to a third aspect to suppress vibration of the driven pulley to thereby improve the durability of the belt and reduce noise. Finally, an object of the invention according to a fourth aspect is to prevent the transmission case from becoming large.
The invention according to the first aspect of this application is a belt type transmission comprising a driving pulley having a fixed pulley piece and a movable pulley piece and fitted to a driving shaft; a driven pulley having a fixed pulley piece and a movable pulley piece and fitted to a driven shaft; and a belt entrained between the driving pulley and the driven pulley for transmitting the power of the driving shaft to the driven shaft, with the driven shaft housed in a rotatably supported transmission case, wherein the fixed pulley piece on the driven side is rotatably supported, respectively, on the driven shaft and the transmission case.
According to the invention of the first aspect, of two places where the fixed pulley piece on the driven side is rotatably supported, one is the transmission case. Therefore, a part of the load from the driven pulley, which has been heretofore imposed only on the driven shaft is imposed on the transmission case. As a result, a load acting on the driven shaft, is reduced, to reduce wear of the support portion of the transmission case that rotatably supports the driven shaft, to thereby improve the durability of the support portion.
The invention of the second aspect is a belt type transmission, wherein the fixed pulley piece on the driven side is supported on the transmission case via a bearing provided between the outer periphery of the fixed pulley piece on the driven side, located radially outwards of the driven shaft, and the inner periphery of the transmission case.
According to the invention of the second aspect, the outer periphery of the fixed pulley piece on the driven side is located radially on the outer periphery of the driven shaft, and the bearing is disposed between the outer periphery thereof and the inner periphery of the transmission case. Therefore, the bearing is to support the load of the driven pulley with a larger area, compared to the case where the driven shaft located radially inwards than the outer periphery of the fixed pulley piece on the driven side is supported, and hence, the pressure acting on the constituent of the bearing can be reduced, to reduce the wear. As a result, in addition to the effects of the invention according to the first aspect, the durability of the bearing can be improved, which supports the fixed pulley piece on the driven side on which the load of the driven pulley acts.
The invention of the third aspect is a belt type transmission, wherein the transmission case is composed of a plurality of constructional elements, and the fixed pulley piece on the driven side is supported by a holder, which is one of the plurality of constructional elements, the holder being coupled to another constructional element of the plurality of constructional elements, and overlapping at least partially only the driven pulley, of the driving pulley and the driven pulley, as seen in the direction along the driven shaft.
According to the invention of the third aspect, it is the holder, being the constructional element of the transmission case, that rotationally supports the fixed pulley piece on the driven side, and the holder is coupled to another constructional element of the transmission case. Moreover, as seen in the direction along the driven shaft, the size of the holder is such that it overlaps only the driven pulley at least partially. Therefore, since a coupling portion of the holder with another constructional element can be located in the vicinity of the driven pulley, the rigidity of the holder having a support portion for supporting the fixed pulley piece on the driven side can be increased, thereby enabling suppression of vibration of the driven pulley.
Moreover, since the holder is a member having such a size overlapping only the driven pulley at least partially, vibration can be suppressed by using a material having high rigidity, different from the material of the other constructional element of the transmission case. Furthermore, even if the material has relatively large specific gravity, since the holder itself can be made small, increase in the weight of the transmission case can be suppressed.
As a result, in addition to the effects of the invention of the first or second aspect, vibration of the driven pulley can be suppressed. As a result, wear at the sliding area between the belt and the driven pulley can be further reduced, to thereby improve the durability of the belt and the driven pulley, and further, noise can be reduced. Moreover, freedom in selection of the material increases from a viewpoint of suppression of vibration, without causing a large increase in the weight, thereby enabling further reduction of vibration and noise.
The invention of a fourth aspect is a belt type transmission, wherein the holder is fitted in a housing hole disposed in other constructional element of the plurality of constructional elements.
According to the invention of the fourth aspect, since the holder is fitted in the housing hole disposed in another constructional element of the transmission case, the holder and the constructional element do not overlap each other, and these can be arranged on substantially the same plane. As a result, in addition to the effects of the invention of the third aspect, a smaller transmission case can be obtained.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.